Content-type: text/html Manpage of uvfix


Section: User Commands (1)
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uvfix - Re-calculate obsra, obsdec and (u,v,w) from radec keyword.  




uv analysis  


UVFIX Re-calculates obsra, obsdec and (u,v,w) from radec keyword. UVFIX does NOT change the phase. use UVCAL to correct the phase to the new phase center. By default, UVFIX applies the calibration files before it processes the uv-data into the output file.  


The names of the input uv data sets. Multiple names can be given, separated by commas. At least one name must be given.
The normal uv selection commands. See the Users manual for details. The default is to process all data. Note that window selection can not be used with options=hanning, passband, contsub, or wide.
Source right ascension and declination. These can be given in hh:mm:ss,dd:mm:ss format, or as decimal hours and decimal degrees. Setting RA and DEC will change the phase center to the RA and DEC specified. The default leaves the data unchanged.
This gives extra processing options. Several options can be given, each separated by commas. They may be abbreivated to the minimum needed to avoid ambiguity. Possible options are:
   'nocal'      Do not apply the gains file.
   'nopass'     Do not apply bandpass corrections.
   'nopol'      Do not apply the polarization leakage file.
   'nowide'     Do not copy across wide-band channels.
   'nochannel'  Do not copy across spectral channels.
   'unflagged'  Copy only those records where there are some
                unflagged visibilites.
   'contsub'    Continuum subtraction using a linear fit to the real
            and imaginary parts of each spectral window.
                Exclude badchan and endchan specified below.
   'conjugate'  Conjugate visibilities
fxcal' Calibrate FX correlator data
            by dividing the cross correlations by the 
            geometric mean of the autocorrelations.
   'hanning'    Hanning smooth each spectral window.
   'holo'       Replace u,v with dra,ddec for holography.
   'linecal'    Remove phase slope across passband due to line length
            changes. This option also corrects the phase difference
            between the wide channels due to line length.
            options=linecal,wide will re-make the wideband from
            the channel data after the phase slope is removed.  
            option can gain in SNR for the wide channels might be
parang' Multiply LR by expi(2*chi) and RL by expi(-2*chi)
            where chi is the parallactic angle for Alt-Az antennas.
   'passband'   Fit passband to lsb and correct the uv-data.
            Can be used when the source is strong. e.g. for
                planets. The passband is estimated from the lsb,
                smoothed within each spectral window, and applied
                to the lsb data. The complex conjugate is applied
            to the usb. This corrects for time variable IF
            passband errors. The uv-data must contain the same
            spectral windows in both sidebands of LO1.
   'uvrotate'   Rotate uv-coordinates from current to standard epoch.
            The standard epoch, ra, dec can be changed using PUTHD.
   'avechan'    Average unflagged spectral channels into wide,2,1 for
            lsb and usb of LO1 respectively. The data are weighted by
            bandwidth and exclude badchan and endchan specified below.
            Also remake wideband average for each spectral window.
   'avewide'    Average unflagged wideband channels into wide,2,1 for
            lsb and usb of LO1 respectively. The data are weighted by
            bandwidth and exclude badchan specified below and wide,2,1

NOTE: Options=nochannel cannot be used with "hanning", "passband" and "contsub". For these 3 options no processing is performed on the wideband data.

Number of ranges of bad channels followed by list of up to 20 pairs of numbers giving range of channels to exclude in options=contsub and options=avechan. E.g. badchan=3,1,3,15,16,256,257 excludes the 3 ranges (1,3) (15,16) and (265,257)
Number of channels to drop from the ends of each spectral window in options=passband, contsub, and avechan. Default=0.
Number of channels to average in options=passband. Default=1.
Rms noise level used to flag data in options=contsub. All channels are flagged if the rms noise level per channel is greater than sigma after subtracting the continuum. Endchan and badchan are not included in computing the rms. The default is sigma=0. which does not flag any data.
Multiply the data and wideband by cmplx(scale1,scale2). Two values. Default is no scaling. If only one value is given it is assumed to be a real value. E.g. scale=0,1 multiplies the data by sqrt(-1)
Subtract a complex valued offset from the uv-data. Two values give itude (after calibrations have been applied by uvcal) phase in degrees. Default is none.
Subtract a source model from the uv-data. Three values give the flux density [Jy], scale [nanosecs], and index for a radial power law:
        model = flux * (uvdist/scale) ** index
The model visibility is subtracted from the uv-data. Default model=0,0,0. i.e. no model is subtracted.
Subtract the source polarization from the uv-data. Two values give polarized intensity, Ip, and position angle, 2*psi, in degrees. Use same amplitude units as uv-data after calibration is applied.. subtract Ip*expi(2*psi)*expi(-2*chi) from LR, and subtract Ip*expi(-2*psi)*expi(2*chi) from RL where chi is the parallactic angle for Alt-Az antennas. Default=0,0. is no correction. After subtracting the source polarization, the averaged uv-data gives the instrumental polarization for each baseline.
Change the polarization code. Default polcode=0 makes no change. Polarizations are YX,XY,YY,XX,LR,RL,LL,RR,-,I,Q,U,V Polarization codes -8,-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4 E.g. polcode=4 changes YX,XY,YY,XX to LR,RL,LL,RR E.g. polcode=-4 changes LR,RL,LL,RR to YX,XY,YY,XX
Rotate uv coordinates and hence image by parot degrees. Rotation is +ve to the E from N. i.e. increasing PA. Default is no rotation.
The name of the output uv data set. No default.




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Time: 18:35:38 GMT, July 05, 2011